1. Field of the Invention
The present invention relates to a projection type display apparatus and, more particularly, to a projection type display apparatus for displaying a full-color image on a display surface such as a screen using a mirror array device as optical modulation means.
2. Related Background Art
Along with the advent of the age of multimedia, image display apparatuses are used in every scene. Generally, display apparatuses for forming an image by modulating light are roughly classified into two types. One type is a direct viewing image type display apparatus such as a direct viewing CRT (Cathode Ray Tube) and direct viewing LCD, and the other type is a projection type display apparatus, including a LCD (Liquid Crystal Display), and a mirror device such as a DMD (Deformable Mirror Device), or AMA (Actuated Mirror Array). Since projection type display apparatuses can easily increase the screen size, front projectors for presentation or the like and rear projectors for a home theater or the like are becoming widely used. In such a projection type display apparatus using a liquid crystal panel or mirror device, the liquid crystal panel or mirror device serving as an optical modulation device is illuminated with light from a light source, and transmitted or reflected light is made incident on a screen or the like through a projecting optical system, thereby forming an image.
Although a direct viewing CRT is excellent in image quality, the weight and volume of the apparatus increase, and the manufacturing cost increases as the screen size increases. To the contrary, a projecting liquid crystal display apparatus can be made relatively thin, and the weight and volume can be reduced because its optical structure is simple. However, since an LCD normally uses linearly polarized light, the light utilization efficiency is as low as 1% to 5%. In addition, liquid crystal molecules respond slowly, and the liquid crystal layer is readily heated.
To solve the above problems, projection type display apparatuses using a mirror device such as a DMD or AMA have been developed. Currently, such projection type display apparatuses can obtain a light utilization efficiency of 5% to 10%. In addition, optical modulation is not affected by the polarization state of incident light and does not affect the polarization state of reflected light.
AMAs serving as mirror devices are roughly classified into a bulk type and a thin-film type. A bulk AMA is disclosed in U.S. Pat. No. 5,469,302 by Dae-Young Lim. To obtain the bulk AMA, a ceramic layer having a multilayered structure is cut into a thin ceramic wafer with a metal electrode formed inside, the ceramic wafer is mounted on an active matrix incorporating a transistor, the resultant structure is fabricated by sawing, and a mirror is formed on it.
A thin-film AMA is disclosed in U.S. Pat. No. 5,815,305. Referring to FIG. 4, the thin-film AMA has an active matrix 31, an actuator 33 formed on the active matrix 31, and a mirror 35 formed on the actuator 33.
The active matrix 31 has a substrate 37, and Mxc3x97N (M and N are positive integers) transistors (not shown) formed on the substrate 37, and Mxc3x97N connection terminals 39 formed on the respective transistors.
The actuator 33 has a support portion 41 formed on the active matrix 31 and having the connection terminal 39, a first electrode 43 whose lower end on one side is attached to the support portion 41 and other side is formed in parallel to the active matrix 31, an interconnection or conductive tube 49 formed in the support portion 41 to connect the connection terminal 39 and first electrode 43, a deformable layer 45 formed on the first electrode 43, a second electrode 47 formed on the deformable layer 45, a spacing member 51 formed on one side of the second electrode 47, and a support layer 53 whose lower end on one side is attached to the spacing member 51 and other side is formed in parallel to the second electrode 47. The second electrode 47 is connected to the active matrix 31 by an interconnection (not shown). The mirror 35 is formed on the support layer 53.
When a predetermined electrical signal (voltage) corresponding to an image signal is applied to the first electrode 43 of each pixel through the active matrix 31, each pixel actuator 33 tilts by a predetermined angle, and accordingly, each pixel mirror 35 tilts.
FIG. 3 shows this state. The pixel mirror 35 tilts by a predetermined amount in accordance with the voltage applied to the first electrode 43, as indicated by an arrow A. The reflecting direction of reflected light of a light beam L incident on the mirror 35 changes in accordance with the tilt amount, as indicated by an arrow B.
Such a thin-film AMA is manufactured using semiconductor manufacturing processes. For this reason, the mirror array has a perfect quality so that light enough to display digital image with a high-luminance and high-contrast under normal indoor illumination conditions can be transmitted to the screen. In other words, a thin-film AMA is a reflection-type optical modulator using a thin-film piezoelectric actuator in relation to a microscopic mirror and has been developed to obtain a tilt angle enough to provide high contrast and a light utilization efficiency enough to provide high luminance. A thin-film AMA has also been developed to ensure uniformity in a large scale integration across 300,000 pixels of mirrors formed from a single pattern.
As for forming a projection type display apparatus using a mirror device such as a thin-film AMA or DMD, a typical arrangement is disclosed in, e.g., Japanese Patent Application Laid-open No. 8-21977. That is, white illumination light is time-divisionally color-separated by a rotary color filter, a mirror device is illuminated with each color light component, and reflected light is guided into or outside the aperture of a projecting lens in accordance with tilt drive of each pixel mirror, thereby obtaining a predetermined full-color projected image.
In the prior art disclosed in Japanese Patent Application Laid-open No. 8-21977, however, in projecting a full-color image, the illumination system has at least a rotary filter, a rotary filter drive motor, and a rotary syndronized signal processing system for color separation, resulting in complex structure. Additionally, since the rotary filter, i.e., a section rotatably driven at a high speed of up to 10,000 rpm is present, the system has problems in vibration noise and reliability.
One aspect of the present invention is to provide a projection type display apparatus comprising:
a mirror array device for performing optical modulation by a plurality of tiltable pixel mirrors;
an illumination optical system for illuminating the mirror array device with a plurality of color light components of different colors from different directions; and a projecting optical system for projecting reflected light components from the mirror array device onto a projected surface, wherein tilt angles of the pixel mirrors have a plurality of angle ranges that do not overlap each other, and one of the plurality of color light components is projected onto the projected surface for each angle range.
An apparatus described above preferably has a feature that each pixel mirror is not tilted to display black on the projected surface.
An apparatus described above preferably has a feature that the tilt angle of each pixel mirror is maximized to display black on the projected surface.
An apparatus described above preferably has a feature that each pixel mirror is tilted by a predetermined angle to display black on the projected surface.
An apparatus described above preferably has a feature that the projecting optical system has an aperture which shields, of the reflected light components from the mirror array device, a light component which is not to be projected onto the projected surface.
An apparatus described above preferably has a feature that the plurality of light components of different colors are red, green, and blue light components, and a color to be displayed on the projected surface is switched between red, green, and blue by switching the angle range including the tilt angle of each pixel mirror.
An apparatus described above preferably has a feature that gray level display of each color is performed by changing the tilt angle of each pixel mirror.
An apparatus described above preferably has a feature that gray level display of each color is performed by changing the tilt angle of each pixel mirror.
An apparatus described above preferably has a feature that color display of one pixel is performed by mixing the color light components from the pixel mirrors by time color mixing.
An apparatus described above preferably has a feature that color display of one pixel is performed by mixing the color light components from the plurality of pixel mirrors adjacent to each other.
An apparatus described above preferably has a feature that the angle ranges include first, second, third, and fourth ranges, when the tilt angle falls within the first range, red is displayed on the projected surface, when the tilt angle falls within the second range, green is displayed on the projected surface, when the tilt angle falls within the third range, blue is displayed on the projected surface, and when the tilt angle falls within the fourth range, black is displayed on the projected surface.
An apparatus described above preferably has a feature that gray level display of each color is performed by changing the tilt angle of each pixel mirror within each angle range.
An apparatus described above preferably has a feature that the pixel mirrors in the mirror array device are simultaneously illuminated with the plurality of color light components of different colors from different directions.
The other aspect of the present invention is to provide a projection type display apparatus comprising:
a mirror array device for performing optical modulation by a plurality of tiltable pixel mirrors; and a projecting optical system for projecting reflected light components from the mirror array device onto a projected surface, wherein tilt angles of the pixel mirrors have a plurality of angle ranges that do not overlap each other, and a color of a light component guided to the projecting optical system by each pixel mirror changes for each angle range.
An apparatus described above preferably has a feature that a color to be guided to the projecting optical system is switched between red, green, and blue by switching the angle range including the tilt angle of each pixel mirror.
An apparatus described above preferably has a feature that gray level display of each color is performed by changing the tilt angle of each pixel mirror.
An apparatus described above preferably has a feature that gray level display of each color is performed by changing the tilt angle of each pixel mirror.
An apparatus described above preferably has a feature that color display of one pixel is performed by mixing the color light components from the pixel mirrors by time color mixing.
An apparatus described above preferably has a feature that color display of one pixel is performed by mixing the color light components from the plurality of pixel mirrors adjacent to each other.
An apparatus described above preferably has a feature that the angle ranges include first, second, third, and fourth ranges, when the tilt angle falls within the first range, red is displayed on the projected surface, when the tilt angle falls within the second range, green is displayed on the projected surface, when the tilt angle falls within the third range, blue is displayed on the projected surface, and when the tilt angle falls within the fourth range, black is displayed on the projected surface.
An apparatus described above preferably has a feature that gray level display of each color is performed by changing the tilt angle of each pixel mirror within each angle range.
An apparatus described above preferably has a feature that the pixel mirrors in said mirror array device are simultaneously illuminated with the plurality of color light components of different colors from different directions.